One unique feature of SPECT is the ability to acquire projection data simultaneously from two or more pharmaceuticals each labeled with a radioisotope emitting photons with different energies, allowing simultaneous measurement of multiple physiological processes such as rest/stress perfusion or perfusion/innervation. This may provide additional diagnostic information and, in addition, there are practical advantages such as increased patient throughput, elimination of problems with registration and results in common patient motion in the two studies. However, due to scatter in the patient and ? camera and the poor energy resolution of conventional gamma cameras, dual isotope acquisition will result in crosstalk contamination of the two sets of projection data. The overall goal of this work has been to develop, optimize and evaluate methods for simultaneously acquiring and reconstructing dual isotope images that can reduce the effects of this crosstalk to the point where the images have diagnostic image quality close to that which they would have if acquired separately. In this application, we focus on two specific applications: dual isotope 99mTc stress/201Tl rest myocardial perfusion SPECT and dual isotope 99mTc perfusion/123I innervation myocardial SPECT. In the previous funding cycles, we have characterized the crosstalk and developed compensation methods. Since these methods allow classifying patients into more than two diagnostic classes, e.g., having normal, ischemic or infracted myocardium, we have developed methods for assessing 3-class image. We have also developed simulation tools, including realistic populations of phantoms and fast methods for simulating realistic SPECT data, for use in optimizing and evaluating the simultaneous acquisition and crosstalk compensation methods. Using these simulation tools, we have performed preliminary optimizations and evaluations of the compensation methods. In these, we have demonstrated that the compensation methods significantly reduce the degradation in image quality due to crosstalk and image quality approaching that from separate acquisition. In this application, we propose to perform rigorous optimization and validation of these methods in order to demonstrate their clinical potential and efficacy. Toward this end, we propose to: (1) further develop 3-class methods for rigorous optimization of the simultaneous acquisition methods;(2) further develop and optimize the crosstalk compensation and simultaneous acquisition methods;(3) rigorously validate rigorously the compensation methods using animal and human studies;and (4) explore the feasibility of simultaneous acquisition from three isotopes. Given the frequency of rest/stress myocardial perfusion SPECT, and the prevalence of heart disease, simultaneous acquisition protocols for myocardial SPECT have a high potential for clinical impact. However, rigorous validation is essential before this clinical potential can be realized. The proposed studies have the potential to provide definitive evidence about the utility of simultaneous acquisition methods, and thus to have a significant impact on patient care. PUBLIC HEALTH RELEVANCE: The goal of this project is to develop, optimize, and evaluate methods for imaging two properties of the heart at the same time. In one subproject we will develop methods to image the blood flow in the heart at rest and when the patient has been stressed;in the other we develop methods to image blood flow and areas where the nerves causing the heart to beat are damaged. These methods have the potential to provide better and cheaper diagnosis of heart problems.